package com.example.demo.util;

import java.security.Key;
import java.security.Security;

import javax.crypto.Cipher;

public class DES {
	private static String strDefaultKey = "abcDEF123";
	private Cipher encryptCipher = null;
	private Cipher decryptCipher = null;


	/**
	 * 默认构造方法，使用默认密钥
	 * @throws Exception
	 */
	public DES() throws Exception {
		this(strDefaultKey);
	}


	/**
	 * 指定密钥构造方法
	 * @param strKey 指定的密钥
	 * @throws Exception
	 */
	public DES(String strKey) throws Exception {
		Security.addProvider(new com.sun.crypto.provider.SunJCE());
		Key key = getKey(strKey.getBytes());
		encryptCipher = Cipher.getInstance("DES");
		encryptCipher.init(Cipher.ENCRYPT_MODE, key);
		decryptCipher = Cipher.getInstance("DES");
		decryptCipher.init(Cipher.DECRYPT_MODE, key);
	}


	/**
	 * 加密字符串
	 * @param strIn 需加密的字符串
	 * @return 加密后的字符串
	 * @throws Exception
	 */
	public String encrypt(String strIn) throws Exception {
		return byteArr2HexStr(encrypt(strIn.getBytes()));
	}


	/**
	 * 加密字节数组
	 * @param arrB 需加密的字节数组
	 * @return 加密后的字节数组
	 * @throws Exception
	 */
	public byte[] encrypt(byte[] arrB) throws Exception {
		return encryptCipher.doFinal(arrB);
	}



	/**
	 * 解密字符串
	 * @param strIn 需解密的字符串
	 * @return 解密后的字符串
	 * @throws Exception
	 */
	public String decrypt(String strIn) throws Exception {
		return new String(decrypt(hexStr2ByteArr(strIn)));
	}


	/**
	 * 解密字节数组
	 * @param arrB 需解密的字节数组
	 * @return 解密后的字节数组
	 * @throws Exception
	 */
	public byte[] decrypt(byte[] arrB) throws Exception {
		return decryptCipher.doFinal(arrB);
	}



	/**
	 * 从指定字符串生成密钥，密钥所需的字节数组长度为8位
	 * 不足8位时后面补0，超出8位只取前8位
	 * @param arrBTmp 构成该字符串的字节数组
	 * @return 生成的密钥
	 * @throws java.lang.Exception
	 */
	private Key getKey(byte[] arrBTmp) throws Exception {
		byte[] arrB = new byte[8];
		for (int i = 0; i < arrBTmp.length && i < arrB.length; i++) {
			arrB[i] = arrBTmp[i];
		}
		Key key = new javax.crypto.spec.SecretKeySpec(arrB, "DES");
		return key;
	}



	/**
	 * 将byte数组转换为表示16进制值的字符串，
	 * 如：byte[]{8,18}转换为：0813，
	 * 和public static byte[] hexStr2ByteArr(String strIn)
	 * 互为可逆的转换过程
	 * @param arrB 需要转换的byte数组
	 * @return 转换后的字符串
	 * @throws Exception 本方法不处理任何异常，所有异常全部抛出
	 */
	public static String byteArr2HexStr(byte[] arrB) throws Exception {
		int iLen = arrB.length;
		StringBuffer sb = new StringBuffer(iLen * 2);
		for (int i = 0; i < iLen; i++) {
			int intTmp = arrB[i];
			while (intTmp < 0) {
				intTmp = intTmp + 256;
			}
			if (intTmp < 16) {
				sb.append("0");
			}
			sb.append(Integer.toString(intTmp, 16));
		}
		return sb.toString();
	}



	/**
	 * 将表示16进制值的字符串转换为byte数组，
	 * 和public static String byteArr2HexStr(byte[] arrB)
	 * 互为可逆的转换过程
	 * @param strIn 需要转换的字符串
	 * @return 转换后的byte数组
	 * @throws Exception 本方法不处理任何异常，所有异常全部抛出
	 */
	public static byte[] hexStr2ByteArr(String strIn) throws Exception {
		byte[] arrB = strIn.getBytes();
		int iLen = arrB.length;
		byte[] arrOut = new byte[iLen / 2];
		for (int i = 0; i < iLen; i = i + 2) {
			String strTmp = new String(arrB, i, 2);
			arrOut[i / 2] = (byte) Integer.parseInt(strTmp, 16);
		}
		return arrOut;
	}

}
